Mortars

From earliest times the usefulness of the mortar as
an arm of the artillery has been clearly recognized. Up until the 1800's
the weapon was usually made of bronze, and many mortars had a fixed
elevation of 45°, which in the sixteenth century was thought to be the
proper elevation for maximum range of any cannon. In the 1750's Müller
complained of the stupidity of British artillerists in continuing to use
fixed-elevation mortars, and the Spanish made a mortero de plancha,
or "plate" mortar (fig. 37), as late as 1788. Range for such a
fixed-elevation weapon was varied by using more or less powder, as the
case required. But the most useful mortar, of course, had trunnions and
adjustable elevation by means of quoins.

FIGURE 36—BRITISH MORTAR ON ELEVATING BED (1740).

The mortar was mounted on a "bed"—a pair of wooden
cheeks held together by transoms. Since a bed had no wheels, the piece
was transported on a mortar wagon or sling cart. In the battery, the
mortar was generally bedded upon a level wooden platform; aboard ship,
it was a revolving platform, so that the piece could be quickly aimed
right or left. The mortar's weight, plus the high angle of elevation,
kept it pretty well in place when it was fired, although British
artillerists took the additional precaution of lashing it down.

FIGURE 37—SPANISH 5-INCH BRONZE MORTAR (1788).

The mortar did not use a wad, because a wad prevented
the fuze of the shell from igniting. To the layman, it may seem strange
that the shell was never loaded with the fuze toward the powder charge
of the gun. But the fuze was always toward the muzzle and away from the
blast, a practice which dated from the early days when mortars were
discharged by "double firing": the gunner lit the fuze of the shell with
one hand and the priming of the mortar with the other. Not until the
late 1600's did the method of letting the powder blast ignite the fuze
become general. It was a change that greatly simplified the use of the
arm and, no doubt, caused the mortarman to heave a sigh of relief.

Most mortars were equipped with dolphins, either
singly or in pairs, which were used for lifting the weapon onto its bed.
Often there was a little bracketed cup—a priming pan—under the vent, a
handy gadget that saved spilling a lot of powder at the almost vertical
breech. As with other bronze cannon, mortars were embellished with
shields, scrolls, names, and other decoration.

About 1750, the French mortar had a bore length 1-1/2
diameters of the shell; in England, the bore was 2 diameters for the
smaller calibers and 3 for the 10- and 13-inchers. The extra length
added a great deal of weight to the British mortars: the 13-inch weighed
25 hundredweight, while the French equivalent weighed only about half
that much. Müller complained that mortar designers slavishly copied what
they saw in other guns. For instance, he said, the reinforce was
unnecessary; it . . . overloads the Mortar with a heap of useless metal,
and that in a place where the least strength is required, yet as if this
unnecessary metal was not sufficient, they add a great projection at the
mouth, which serves to no other purpose than to make the Mortar
top-heavy. The mouldings are likewise jumbled together, without any
taste or method, tho' they are taken from architecture." Field mortars
in use during Müller's time included 4.6-, 5.8-, 8-, 10-, and 13-inch
"land" mortars and 10- and 13-inch "sea" mortars. Muller, of course,
redesigned them.

FIGURE 39—COEHORN MORTAR. The British General Oglethorpe used 20
coehorns in his 1740 bombardment of St. Augustine. These small mortars
were also used extensively during the Civil War.

The small mortars called coehorns (fig. 39) were
invented by the famed Dutch military engineer, Baron van Menno Coehoorn,
and used by him in 1673 to the great discomfit of French garrisons.
James Oglethorpe had many of them in his 1740 bombardment of St.
Augustine when the Spanish, trying to translate coehorn into their own
tongue, called them cuernos de vaca—"cow horns." They continued
in use through the U.S. Civil War, and some of them may still be seen in
the battlefield parks today.

Bombs and carcasses were usual for mortar firing, but
stone projectiles remained in use as late as 1800 for the pedrero class
(fig. 43). Mortar projectiles were quite formidable; even in the
sixteenth century missiles weighing 100 or more pounds were not
uncommon, and the 13-inch mortar of 1860 fired a 200-pound shell. The
larger projectiles had to be whipped up to the muzzle with block and
tackle.

FIGURE 40—THE "DICTATOR." This huge 13-inch mortar was used by the
Federal artillery in the bombardment of Petersburg, Va., 1864-65.

In the last century, the bronze mortars metamorphosed
into the great cast-iron mortars, such as "The Dictator," that mammoth
Federal piece used against Petersburg, Va. Wrought-iron beds with a pair
of rollers were built for them. In spite of their high trajectory,
mortars could range well over a mile, as witness these figures for
United States mortars of the 1860's, firing at 45° elevation:

Ranges of U. S. Mortars in 1861

Caliber

Projectile
weight (pounds)

Range
(yards)

8-inch siege

45

1,837

10-inch siege

90

4,625

12-inch seacoast

200

2,100

13-inch seacoast

200

4,325

At the siege of Fort Pulaski in 1862, however,
General Gillmore complained that the mortars were highly inaccurate at
mile-long range. On this point, John Müller would have nodded his head
emphatically. A hundred years before Gillmore's complaint, Müller had
argued that a range of something less than 1,500 yards was ample for
mortars or, for that matter, all guns. "When the ranges are greater,"
said Müller, "they are so uncertain, and it is so difficult to judge how
far the shell falls short, or exceeds the distance of the object, that
it serves to no other purpose than to throw away the Powder and shell,
without being able to do any execution."